Decubitus ulcers, commonly called "bed sores," occur in bed-ridden persons who cannot move sufficiently frequently in ways to relieve pressure upon the skin at locations on the body where there is very little tissue between a bone and the skin. The sacrum (base of the spine), trochanteric regions (the ends of the pelvis), ankles, and heels are places where bed sores most frequently occur; there are other places on the body where bed sores can occur. Bed sores occur where the surface supporting the body bears on the skin, as over a bony prominence of the body, to restrict capillary blood flow in the skin sufficiently that skin tone breaks down and open sores occur as a result. Bed sores can be prevented by periodically relieving body-supporting forces on the body in such places so that capillary flow can be reestablished enough to prevent serious loss of skin tone.
Air-inflated pads for preventing bed sores have been described in numerous patents and other publications, and are commercially available. Such pads can be considered to be a special class of air mattress in which two or more sheets of air-impermeable material, such as flexible synthetic plastic film, are secured together to define between them two or more sets of alternately located chambers. The several sets of chambers are coupled, as by separate air hoses, to an air supply device which operates to pressurize and inflate, at different times according to a desired schedule, the different sets of chambers in the pad. As one set of chambers is inflated, the other chambers are deflated. Such pads, commonly known as alternating pressure pads (sometimes also called alternate pressure pads), are placed between a bed-ridden person and the conventional mattress of the bed on which the person lies. In use of such pads, the locations where supporting forces are applied to the body are alternated in a cyclic manner on a schedule intended to allow constricted skin capillaries to reopen for blood flow through them long enough to maintain the skin in good condition before body supporting forces are reapplied to the skin for a time.
Alternating pressure pads previously constructed or described, as a rule, define the alternately inflatable chambers so that they are of substantially equal size (width or diameter) over the extent of the pad. Heretofore, it has not been effectively recognized that heels in particular are especially prone to the occurrence of bed sores, more so than other areas of the body, due to the large loads which heels support in a person lying on his back and due to the highly curved and projecting nature of the heel. There is a need for improvement in such pads in the areas thereof placed under the lower limbs of a person. To the extent previously constructed or described pads have arrangements for lower limb support different from torso and head support, they have not yet effectively addressed this need.
Also, alternating pressure pads cause persons supported on them to tend to become damp on those surfaces of their bodies facing the pads. This occurs because such a pad, being made of air-impermeable material, cannot breathe or permit air flow in the same manner as a conventional mattress can breathe or permit air flow. Body surfaces facing toward such a pad become hot, so the person perspires in those parts of his body and so becomes damp and uncomfortable. Also, skin dampness enhances the tendency for bed sores and other problems to develop. To counteract such problems, it is known to construct alternating pressure pads for flow of body cooling air from them toward the supported person by providing very small air flow holes through the top of the pad from at least some of the alternately inflatable body supporting chambers in the pad. It is also known to overlay such body cooling pads with a layer of foam rubber or the like to cause air discharged into the foam from the body supporting chambers to diffuse through the foam and to emerge over a larger area of the foam toward the patient, and at a lower velocity.
Previously known body cooling alternating pressure pads present several difficulties. Such a pad is always a body cooling pad. Very often, for any of a number of reasons, it may be desirable to cease the flow of body cooling air from the pad. That cannot be done without loss of the alternate pressure support function which is needed to prevent bed sores. It is therefore necessary to have two pads available, one with the body cooling function and one without that function, so that pads can be changed depending on whether body cooling is or is not needed. Pad changing can be distressing to the bedridden person and requires the services of at least one other person. A need exists for an alternating pressure pad which can be operated in cooling and non-cooling modes; such a pad, among other advantages, can be used under varying conditions which presently can be addressed only by the use of separate pads having and not having body cooling features.